EVALUATION OF THROMBOTIC RISK IN PATIENTS WITH POSITIVE ANTIPHOSPHOLIPID ANTIBODIES WITHOUT CLINICAL CRITERIA OF THE DISEASE 153 R. Demetrio Pablo1, P. Muñoz2, V. Calvo-Río3, L. Riancho-Zarrabeitia* 3, M. López-Hoyos4, V. M. Martínez-Taboada3 1Ophtalmology, 2Primary Care Management, 3Rheumatlogy, 4Immunology, Hospital Universitario Marqués de Valdecilla. IDIVAL. Facultad Medicina. UC, Santander, Spain BACKGROUND RESULTS The prevalence of thrombosis in antiphospholipid syndrome (APS) and the factors associated with thrombosis vary depending on the population studied. Although aPL have a strong relationship with thrombosis and pregnancy morbidity, the value of each type of aPL as a marker to develop APS it is not fully clarified. After a mean follow-up of 146±60.3 months, of the 138 patients included in the study, 13 (9.4%) developed thrombosis. The mean time to thrombotic episode was 81.4±41.7 months. Several classic cardiovascular risk factors (CVRF) such as tobacco (61.5% in thrombosis group vs 23.2% in the group without thrombosis; p=0.003), hypertension (53.8% vs 15.3%;p=0.001) and dyslipidemia (DLP) (38.5% vs 5.6%;p=0.001) were more frequent in patients with thrombosis. These 3 classic CVRF were independent risk factors for thrombosis in the univariate analysis, with an OR of 6.5 (95%CI 2.0-21.3) for hypertension, 5.3 (95%CI 1.6-17.5) for tobacco and 10.5 (95%CI 2.7-40.8) for DLP. Regarding the different antibodies, only the lupus anticoagulant (LA) (p=0.062) and anticardiolipin antibodies (aCL) IgM (p=0.14) tended to be more frequent in patients with thrombosis. Positivity for the 3 types of antibodies (AL, aCL, AB2GPI) was associated with increased risk of thrombosis (OR 7 [95%CI 1.9-28.5]; p=0.004). Multivariate analysis showed as independent risk factors for thrombosis: smoking (OR 8.3 [95%CI 1.3-52.5]; p=0.024), hypertension (OR 15.9 [95%CI 1.8-138.7]; p=0.012), DLP (OR 16.9 [95%CI 1.4-108.3]; p=0.027) and IgM aCL (OR 18.7 [95%CI 12-277.7]; p=0.033). 13 thrombotic events: 10 arterial: 4 acute myocardial infarctions, 2 thrombosis of central retinal artery, 2 OIN, 1 transient ischemic attack and 1 stroke. 3 thrombosis occurred in venous territory as deep venous thrombosis of lower extremities, with secondary pulmonary thromboembolism in 2 patients. Treatment: 102 patients received prophylaxis with ASA 100 mg, showing a tendency towards protection (OR 0.774 [95%CI 0.2-2.7]; p=0.686). OBJECTIVES To analyze the incidence of thrombosis in patients with positive aPL that do not meet clinical criteria for disease. To identify potential risk factors for thrombosis. To analyze the possible protective role of primary thromboprophylaxis. METHODS Retrospective study of patients with positive aPL on at least 2 times, separated by a minimum of 12 weeks in medium or high titers without fulfilling clinical criteria for APS. The patients were selected from the database of the Department of Immunology of a tertiary hospital (1999- 2004). The presence of vascular event was confirmed through imaging tests. Cases of ischemic optic neuropathy (ION) were diagnosed by clinical and electrophysiological testing. Table 1. Multivariate analysis including classical cardiovascular risk factors and cardiolipin IgM antibodies with the ENTER method.   OR (IC) P TOBACCO 8,3 (1,3-52,6) 0,024 HTA 15,9 (1,8-138,7) 0,012 DLP 16,9 (1,4-208,3) 0,027 IgM aCL 18,8 (1,3-277,7) 0,033 Figure 1. Frequency of different antibodies between the group of patients with thrombosis and without thrombosis, expressed in%. CONCLUSIONS The incidence of thrombosis in patients with positive aPL that do not meet clinical criteria for the disease is about 10%. Tobacco use, DLP, hypertension and IgM aCL are independent risk factors. Higher autoantibody load increases the risk of thrombosis. The protective role of aspirin in this population seems limited and may raise primary thromboprophylaxis with oral anticoagulation in patients considered as high risk.